Following the development of very large-scale digital integrated circuit (VLSI) technology, the radio communication field has experienced two transformations from analog to digital and from stationary to mobile. However, the radio communication field continuously has many problems derived from, for example, the coexistence of a plurality of communication systems, the fierce competition of various standards, and the pressing for frequency resources, etc. To solve these problems, it is much desirable to have the third transformation in the radio communication field from hardware to software and from a narrow-band system to a wide-band system.
An inevitable trend of the development of a base station system is a wide-band base station. The benefit brought by the wide-band base station is that it is easy to produce, with low cost, more functions and better performance. Generally, a radio base station system is capable of operating multiple carriers simultaneously by using wide-band software. It is required that under the premise of not modifying the hardware, the number of multiple carriers (within the capacity range designed) required by the user can be satisfied by setting the software. To accomplish this, the entire base station is designed according to the maximum capacity, and when it is used practically, a proper number of multiple carriers in a digital intermediate frequency band or a base frequency band portion are closed off to satisfy the number of multiple carriers required by the user. However, in a wide-band system, the portions from an intermediate frequency to an antenna feed are common portions. Thus, the above solution would not use these portions efficiently, thereby causing low operation efficiency and high operation cost of a base station.
Generally, to expand the coverage of a base station, it is desired to have transmission power of the respective carriers as high as possible. It is also desired that a wide-band base station has the ability of increasing output power of the respective carriers under a condition that a full configuration of the base station is not used, for example, a number of multiple carriers in a digital intermediate frequency band or a base frequency band portion are closed off to satisfy the number of multiple carriers required by the user.